Ceramic article and method of manufacture

ABSTRACT

The present invention includes a method of preparing a ceramic precursor article, the ceramic precursor made thereby, a method of making a ceramic article and an article made by that method. It also includes a method of replicating a ceramic shape.

BACKGROUND OF THE INVENTION

In many areas of technology, ceramic products are being used for theirinert properties and heat resistance.

Many Rapid Prototyping processes have been developed in recent years andmany more are currently being researched, but until recently, few ofthem have been used to fabricate ceramic objects.

One of the main challenges of the use of ceramic products with moderntechnologies is its reduction factor (shrinkage). Depending on theprocess used, drying, firing or hot pressing of a ceramic object cancause shrinkage as high as 20 percent. Such shrinkage can be asignificant problem if the nature of the ceramic article requiresprecise dimensional control.

One of the first patents pertaining to the background of the presentinvention was obtained by Bredt et al. and is entitled “Method of threedimensional printing” (U.S. Pat. No. 5,902,441), May 11, 1999. Thispatent described the use of ink-jet print heads to deliver an aqueoussolvent to a powder in cross-sections. This patent describes the basictechnology of printers that may be used in accordance with the presentinvention, such as those commercially available from Z-corp ofBurlington, Mass. A subsequent patent obtained by Bredt et al. andentitled “Method of three dimensional printing” (U.S. Pat. No.7,087,109), Aug. 8, 2006 further describes the use of three-dimensionalprinter systems. Subsequent patents by Jialin Shen (U.S. Published Pat.Appl. 20020016387; 2002) and Kenneth Newell (U.S. Published Pat. Appl.20040081573; 2004) describe means of producing more stable, stronger,and more durable RP objects through various combinations of binder andsolvent. Newell's method produces a “green object,” an unfired ceramicnegative for use as a mold for injected metal. Improvements in Newell'smold-making methods are found in subsequent patents by Bardes, BrucePaul et al (U.S. Published Pat. Appls. 20040151935, 20040152581 and20050252631; 2004 and 2005) and Lynch, Robert F. et al. (U.S. PublishedPat. Appl. 20050281701; 2005).

An article entitled “Rapid Prototyping with Ceramics” by Elizabeth A.Judson & Thomas L. Starr of the Materials Science and Engineering of theGeorgia Institute of Technology (found athttp://www.pelcorcom/library/judson_starr/) explains the use of“Injection Molding and Stereolithography” for the creation of molds forcasting purposes.

A publication entitled “The CAM-LEM Process” (found athttp://dora.eeap.cwru.edu/camlem/camproc.html) explains how layers ofceramic material can be cut with the use of a computer assisted lasercutter and then stacked and fused in order to obtain a final ceramicarticle.

Notwithstanding these developments, there remains a need for methods ofmaking shaped ceramics in an efficient manner while reducing theshrinkage attendant to prior art techniques. Some of the improvementssought to the prior art include apparatus, methods and compositions thatare capable of producing ceramic precursors with high green strength andmore accurate final ceramic shapes with a high degree of veracity to thedesired shape, such as through the reduction in shrinkage anddistortion. Ceramics produced in accordance with the present inventionmay also have relatively reduced porosity compared to ceramics fromother methods.

SUMMARY OF THE INVENTION

The method of the present invention may be carried out using a versionof the Massachusetts Institute of Technology's patented 3DP(Three-Dimensional Printing). The powder-based build system used inaccordance with one embodiment of the invention preferably employsink-jet technology to apply a specific ceramic binder to thin layers ofceramic precursor powder (typically clay powder), rapidly buildingobjects from digital 3D drawing files.

It has been discovered that 3DP processes using certain organicingredients such as cellulose in the ceramic powder used as a two partbinder in preceding technologies (including those described in patentssuch as those described herein) causes a greater reduction in the finalobject than is normal in traditional ceramic object making. Due to thecombustible nature of these organic binders, the object was left with aporous structure that sometimes caused it to collapse or sufferdeformations when exposed to the high heat of the bisque. In order todecrease the reduction factor and increase the object's density, thepresent invention allows for the production of a ceramic-specific binderthat does not require the addition of solid organic binding material toclay recipes. The final objects conform to the standards of traditionalceramics and thus can be used in a multitude of fashions similar totraditional ceramics.

The present invention includes a ceramic precursor article that may befired into a finished ceramic article of a desired shape that may bepredetermined, a method of making the precursor, a method of making thefinished ceramic article, and the finished ceramic article made thereby.

Ceramic Precursor Article

In general terms, the present invention may be described as including aceramic precursor article having a predetermined shape, the articlecomprising alternately deposited layers of (1) a ceramic precursorpowder and (2) a binder comprising water and polyvinyl alcohol, in apre-determined pattern, such that the ceramic precursor article is ofthe predetermined shape.

The ceramic precursor powder may comprise any combination of one or moreclays and other ancillary material(s) (preferably so as to haveplasticity; i.e., workability to be able to take and hold a shapethrough firing), such as feldspar, refractory cement and/or frit toproduce a powder that may be handled and deposited using 3DP equipment,and capable of producing a ceramic precursor article in combination withone or more binder compositions. Preferably, the ceramic precursorpowder additionally comprises clay and at least one silicate, mostpreferably sodium silicate. Also the ceramic precursor powder preferablyhas the plasticity associated with clays, that being the characteristicof being able to be formed into a shape and maintain that shape throughthe firing process. Such materials are also well adapted to accept andhold glaze.

A preferred formula of the ceramic precursor powder comprises:

-   -   (a) from about 50% to about 80% clay;    -   (b) from about 5% to about 20% feldspar;    -   (c) from about 2% to about 10% refractory cement;    -   (d) from about 2% to about 10% frit; and    -   (e) from about 0.5% to about 4% sodium silicate.

In a preferred embodiment the ceramic precursor article comprisesalternately deposited layers of (1) a ceramic precursor powder and (2) abinder substantially free of cellulose, in a pre-determined pattern,such that the ceramic precursor article is of the predetermined shape.

It is preferred that the binder comprises polyvinyl alcohol (PVA). It ispreferred that the polyvinyl alcohol have a molecular weight in therange of 7,000 to about 15,000, and most preferably in the range of fromabout 9,000 to about 10,000, so as not to be too viscous for use in a3DP machine and process. It is also preferred that the polyvinyl alcoholhaving a degree of hydrolysis in the range of from about 65% to about95%, and most preferably in the range of from about 75% to about 85%.Such polyvinyl alcohols are commercially available from Sigma-Aldrich ofSt. Louis, Mo.

The binder may also include one or more humectants, such as glycerol,and one or more flow agents, such as ethylene glycol.

It is preferred that the binder comprises, and preferably consistsessentially of, polyvinyl alcohol from about 60 to about 80%, glycerolfrom about 15 to about 25% and ethylene glycol from about 5 to about 15%by weight of the binder absent water. Most preferably, the bindercomprises polyvinyl alcohol from about 70 to about 75%, glycerol fromabout 15 to about 25% and ethylene glycol from about 5 to about 15% byweight of the binder absent water.

Most preferably, the binder is substantially free of cellulose. Thebinder may also be in the form of aqueous clay slurry.

The ceramic article made from the ceramic precursor article shrinks lessthan 15%, and most preferably less than 10%, as compared to its actualsize upon being subjected to sufficient heat to form a ceramic articletherefrom.

Method of Preparing a Ceramic Article

The method of the present invention may be described as preparing aceramic article of a desired final shape comprising: (a) alternatelydepositing layers of (1) a ceramic precursor powder as described hereinand (2) a binder comprising water and polyvinyl alcohol as describedherein, in a pre-determined pattern so as to form a ceramic precursorarticle of a precursor shape from a plurality of the layers, and (b)subjecting the ceramic precursor article to heat for sufficient time toform a ceramic article of the desired final shape.

The method of the present invention is capable of producing a ceramicarticle made from the ceramic precursor article that shrinks less than15%, and most preferably less than 10%, as compared to its actual size,upon being subjected to sufficient heat to form a ceramic articletherefrom.

The method of the present invention also includes a method of preparinga ceramic article of a desired final shape using a computer-drivenprototyping device having a microprocessor adapted to guide its action,the method comprising: (a) obtaining digital data reflecting the desiredshape; (b) applying the digital data to a microprocessor so as to guidethe action of the computer-driven three-dimensional prototyping deviceto alternately deposit layers of (1) a ceramic precursor powder asdescribed herein and (2) a binder comprising water and polyvinyl alcoholas described herein, in a pre-determined pattern so as to form a ceramicprecursor article of the desired final shape from a plurality of thelayers, and (c) subjecting the ceramic precursor article to heat forsufficient time to form a ceramic article of the desired final shape.

The method of the present invention also includes preparing a ceramicarticle of a desired final shape using a computer-driven prototypingdevice having a microprocessor adapted to guide its action, the methodcomprising: (a) obtaining digital data reflecting a first portion of thedesired shape; (b) obtaining digital data reflecting a second portion ofthe desired shape; (c) applying the digital data to a microprocessor soas to guide the action of the computer-driven prototyping device toalternately depositing layers of (1) a ceramic precursor powder asdescribed herein and (2) a binder comprising water and polyvinyl alcoholas described herein, in a pre-determined pattern so as to form ceramicprecursor articles of the first and second portion of the desired shapefrom a plurality of the layers, and (d) subjecting the ceramic precursorarticle to heat for sufficient time to form a ceramic articles of thefirst and second portion of the desired shape; and (e) assembling theceramic articles of the first and second portion of the desired shapeinto ceramic article of the desired shape.

The present invention also includes a ceramic article of manufacturemade in accordance with the method of the present invention as describedherein.

With respect to the ceramic precursor powder, the present invention mayemploy any ceramic powder that may be deposited using a 3DP layeringtechniques and devices. For example, the ceramic precursor powderpreferably comprises: (a) from about 50% to about 80% clay; (b) fromabout 5% to about 20% feldspar; (c) from about 2% to about 10%refractory cement; and (d) from about 2% to about 10% frit.

A preferred ceramic recipe is: (a) from about 20% to about 30% OM4; (b)from about 20% to about 30% Cedar Height; (c) from about 20% to about30% Fire Clay; (d) from about 10% to about 20% Neph Sy; (e) from about2% to about 7% Sar Bond; and (f) from about 2% to about 7% 3134 Frit.The most preferred amount of these components is (a) about 25% OM4; (b)about 25% Cedar Height; (c) about 25% Fire Clay; (d) about 15% Neph Sy;(e) about 5% Sar Bond; and (f) about 5% 3134 Frit.

The ceramic precursor powder of the present invention may also includeat least one silicate, such as sodium silicate in an amount in the rangeof from about 0.5% to about 4% by weight of the total powder.

The binder of the present invention is principally formed using anaqueous solution/suspension comprising polyvinyl alcohol, with theoptional inclusion of other components such as one or more humectants asare known in the art for the binder to help prevent too much evaporationof the solution (such as glycerol) and a flow agent or viscositymodifier, as are known in the art, that helps with the flow rate of thebinder, to make it possible to increase the binding action (such asethylene glycol).

The preferred binder composition includes polyvinyl alcohol, glyceroland ethylene glycol, in addition to the solvent, such as water.

The preferred ratio ranges for each of these components is polyvinylalcohol to glycerol to ethylene glycol are from about 5:1:1 to about3:2:1. The preferred ranges for each of these components where they arethe only components other than water is polyvinyl alcohol from about 60to about 80%, glycerol from about 15 to about 25% and ethylene glycolfrom about 5 to about 15% by weight of the binder not including theliquid water portion. The preferred amount of these components ispolyvinyl alcohol 70%, glycerol 20% and ethylene glycol 10% by weight ofthe binder not including the liquid water portion. It is preferred thatthe binder composition consist essentially of polyvinyl alcohol andwater. It is also preferred that the binder composition consistessentially of polyvinyl alcohol and water, and at least one humectant,such as glycerol. It is most preferred that the binder compositionconsist essentially of polyvinyl alcohol and water, at least onehumectant, such as glycerol, and at least one flow agent, such asethylene glycol.

Another variation of the present invention is the use of a binder thatmay include one or more a sugars in an amount in the range of from about100 g to about 500 g per liter of water of the binder solution, andpreferably in an amount in the range of from about 250 g to about 350 gper liter of water. The preferred sugar is sucrose, although othersugars may be used. This binder variation may include other optionalcomponents such as sodium polymethacrylate such as in an aqueoussolution such as Darvan (74-76 percent by weight water and 24-26 percentby weight sodium polymethacrylate). The preferred amount of Darvanliquid is in the range of from about 15 to about 26 ml per 1000 ml ofwater, and most preferably about 20 ml per 1000 ml of water. Otheroptional components include calgon liquid detergent, and sodium silicateor colloidal silica. The binder may also include relatively smallamounts of carboxymethylcellulose (CMC). These optional ingredients mayserve as wetting agents or provide additional binding strength. Examplesof binder formulations of this variation include: (a) water 1500 ml (b)Darvan 30 ml; (c) sucrose 400 g and (d) a few drops of dye to identifythe product. Another variation on the same recipe with differentingredients and proportions for instance may be: (a) water 1500 ml (b)CMC 50 ml; (c) sucrose 500 g and (d) a few drops of dye to identify theproduct.

The present invention also includes a ceramic precursor article having apredetermined shape, the article comprising alternately deposited layersof (1) a ceramic precursor powder and (2) a binder comprising watersugar, in a pre-determined pattern, such that the ceramic precursorarticle is of the predetermined shape. It is preferred that the binderbe substantially free of cellulose. The present invention may alsoincludes a ceramic precursor article having a predetermined shape, thearticle comprising alternately deposited layers of (1) a ceramicprecursor powder and (2) a binder substantially free of cellulose, in apre-determined pattern, such that the ceramic precursor article is ofthe predetermined shape.

It is preferred that the binder composition consist essentially of sugarand water. It is also preferred that the binder composition consistessentially of sugar and water at least one humectant as are known inthe art, such as glycerol. It is most preferred that the bindercomposition consist essentially of polyvinyl alcohol, at least onehumectant, such as glycerol, and at least one flow agent as are known inthe art, such as ethylene glycol.

The binder thus preferably comprises an aqueous solution or slurry ofthe components as described above.

It is preferred that the ceramic precursor article shrinks less than 15%as compared to its actual size upon being subjected to sufficient heatto form a ceramic article therefrom, and most preferably less than 10%.

The present invention also includes a method of preparing a ceramicarticle of a desired final shape comprising: (a) alternately depositinglayers of (1) a ceramic precursor powder as described herein and (2) abinder comprising water, sugar and sodium silicate as described herein,in a pre-determined pattern so as to form a ceramic precursor article ofa precursor shape from a plurality of the layers, and (b) subjecting theceramic precursor article to heat for sufficient time to form a ceramicarticle of the desired final shape.

It is preferred that the ceramic precursor article shrinks less than 15%as compared to its actual size upon being subjected to sufficient heatto form a ceramic article therefrom, and most preferably less than 10%.It is likewise preferred that the desired final shape differs from theprecursor shape by less than 15%, preferably less than 10%, and thatmost preferably the desired final shape differs is substantially thesame as the precursor shape.

The present invention also includes a method of preparing a ceramicarticle of a desired final shape using a computer-driven prototypingdevice having a microprocessor adapted to guide its action, the methodcomprising: (a) obtaining digital data reflecting the desired shape; (b)applying the digital data to a microprocessor so as to guide the actionof the computer-driven prototyping device to alternately depositinglayers of (1) a ceramic precursor powder and (2) a binder substantiallyfree of organic material, in a pre-determined pattern so as to form aceramic precursor article of the desired final shape from a plurality ofthe layers, and (c) subjecting the ceramic precursor article to heat forsufficient time to form a ceramic article of the desired final shape.

The method of the present invention also includes a method of preparinga ceramic article of a desired final shape using a computer-drivenprototyping device having a microprocessor adapted to guide its action,the method comprising: (a) obtaining digital data reflecting a firstportion of the desired shape; (b) obtaining digital data reflecting asecond portion of the desired shape; (c) applying the digital data to amicroprocessor so as to guide the action of the computer-drivenprototyping device to alternately depositing layers of (1) a ceramicprecursor powder as described herein and (2) a binder as describedherein, in a pre-determined pattern so as to form ceramic precursorarticles of the first and second portion of the desired shape from aplurality of the layers, and (d) subjecting the ceramic precursorarticle to heat for sufficient time to form a ceramic articles of thefirst and second portion of the desired shape; and (e) assembling theceramic articles of the first and second portion of the desired shapeinto ceramic article of the desired shape.

Method Of Preparing a Ceramic Article Precursor within Compression Step

The present invention also includes a method of preparing a ceramicarticle precursor by the sequential alternative application of layers ofmaterial as follows: (a) a layer of a ceramic precursor powder; and (b)a layer of an aqueous liquid binder solution having at least onewater-soluble binder dissolved in water; so as to form a sequentialmaterial layer having an original thickness; and (c) compressing eachsequential material layer so as to reduce the original thicknessthereof, prior to the deposition of a subsequent sequential materiallayer; so as to form a ceramic precursor article.

Method of Preparing a Ceramic Article within Compression Step

The present invention further includes a method of preparing a ceramicarticle of a desired final shape comprising: (a) alternately depositinglayers of (1) a ceramic precursor powder and (2) a binder, such as onecomprising water and polyvinyl alcohol, each the alternate layers (1)and (2) having an original thickness, in a pre-determined pattern so asto form a ceramic precursor article of a precursor shape from aplurality of the layers, (b) following each deposition of layers (1) and(2), compressing each the alternate layer so as to reduce its originalthickness; and (b) subjecting the ceramic precursor article to heat forsufficient time to form a ceramic article of the desired final shape.

This method has the effect of compacting the layers as they are formed,so as to place the constituent materials in more intimate contact. Thisleads to a stronger ceramic precursor article and ultimately to afinished ceramic that has reduced shrinkage and porosity.

The compression step my be performed by an apparatus as describedherein, as well as by any other apparatus that is capable of providingcontrollable compression force to the object being formed withoutdisrupting its intended shape.

Compression Apparatus—Apparatus for Preparing a Ceramic ArticlePrecursor within Compression Step

Also part of the present invention is an apparatus for preparing aceramic article precursor by the sequential alternative application oflayers of material as follows: (a) a supply bed adapted to contain asupply of a ceramic precursor powder and a powder supply head adapted totransport and deposit layers of the ceramic precursor powder; (b) abinder depositor adapted to produce a patterned layers of a liquid anaqueous liquid binder solution having at least one water-soluble binderdissolved in water; (c) a build table positioned and adapted to acceptalternating layers of the ceramic precursor powder from the powdersupply head, and the aqueous liquid binder solution from the binderdepositor; and to be lowered following each layer deposition; and (d) atamper member adapted to compress successive alternating layers of theceramic precursor powder and the aqueous liquid binder solution, so asto reduce the original thickness thereof.

It is preferred that the tamper member be actuated by a motor controlledby microprocessor or other control apparatus that applies an algorithmadapted to calculate the required dimensions of a given binder layer bydetermining the change in the original thickness of a binder/powderlayer, and adjusting the dimensions of subsequent binder layersaccording to the reduction in overall height of the ceramic precursor asit is being built. That is, the algorithm determines the binder layerpattern next required in sequence based upon the regression in thebuild-up brought about by the know reduction in overall height of theobject (based upon the controlled tamping compression of each layer)after each compression step.

This method may be used to prepare arrangements of more than one ceramicpiece, such as may be required in ceramic constructions of any kind,such as anything from artistic forms, installations and murals, ormulti-piece industrial constructions and arrangements where suchmulti-piece constructions are required or desirable. Examples mayinclude filter arrangements, protective ceramic tiles, bricks, etc., andceramic pieces having more than one piece that fit together, such ascontainers. Accordingly, the present invention allows for the creationof clay body formulas and binder recipes for use in a rapid prototypingprocess, consistent with industry standards for other types of ceramicfabrication, and processes including pottery, tile and brick.

The present invention also includes a ceramic article of manufacturemade in accordance with the method of the present invention as describedherein.

In accordance with the present invention, ceramic precursor articles maybe successfully rendered and then fired at high temperature (i.e., usingtraditional kilns at temperatures of 1500-2000 degrees C.) to obtainceramic positives. The ceramic article may be treated with any glazingas is known and applied in the art.

The objects produced in accordance with the present invention may beused to demonstrate the possible applications of this process. Theceramic objects obtained by this process have evidenced an averagereduction of 15% and some have been subject to different types ofglazing and surface treatments, as are known and applied in this field.

BRIEF DESCRIPTION OF THE DRAWINGS

The file of this patent contains at least one drawing executed in color.Copies of this patent with color drawing(s) will be provided by thePatent and Trademark Office upon request and payment of the necessaryfee.

FIG. 1 is a perspective view of an apparatus in accordance with oneembodiment of the present invention.

FIG. 2 is a perspective view of an apparatus in accordance with oneembodiment of the present invention.

FIG. 3 is a perspective view of an apparatus in accordance with oneembodiment of the present invention.

FIG. 4 is a detailed perspective view of an apparatus in accordance withone embodiment of the present invention.

FIG. 5 is a detailed perspective view of an apparatus in accordance withone embodiment of the present invention.

FIG. 6 is a detailed perspective view of an apparatus in accordance withone embodiment of the present invention.

FIG. 7 is a detailed perspective view of an apparatus in accordance withone embodiment of the present invention.

FIG. 8 is a perspective view of an original article that may bereproduced in accordance with one embodiment of the present invention.

FIG. 9 is a perspective view of a ceramic article prepared as a copy ofthe original article of FIG. 8, in accordance with one embodiment of thepresent invention.

FIG. 10 is a perspective comparative view of the original article ofFIG. 8 and the ceramic article shown in FIG. 9.

FIG. 11 is a perspective view of an article made in accordance with oneembodiment of the present invention.

FIG. 12 is a perspective view of another article made in accordance withone embodiment of the present invention.

FIG. 13 is a perspective view of test bars in accordance with oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the foregoing summary, the following present adetailed description of the present invention, which is presentlyconsidered to be the best mode thereof.

As an example of the present invention, a digital representation ofMartin Newell's teapot was prepared obtained. This is a shape commonlyused in computer graphics, 3D modeling, and 3D animation. A teapot is achallenging object to experiment with for its shape and form within thecontext of 3D software development. That same teapot serves as anexcellent subject model to demonstrate the present invention.

The present invention allows for the fabrication of an article, such asa teapot, accurate in dimensions to the desired shape, and thus theproduction of sculptural objects and other object applications arepossible. In accordance with the present invention, it is feasible tocreate a virtual 3D design that can become a functional object made ofdurable ceramic materials without the need to first prepare a prototypefrom which a mold is made. Rather, the present invention allows for thedirect formation of a finished ceramic piece without the need forprototyping and mold making.

The use of binders and clay formulas of the present invention allow forthe 3DP rapid prototyping processes and apparatus to be used toefficiently prepare final shaped ceramic pieces.

One of the aspects of the present invention is the creation of clay bodyformulae and binder recipes for use in a rapid prototyping process,consistent with industry standards for other types of ceramicfabrication and treatment processes, including those used to makepottery, tile and brick.

The testing standards can be organized around three main components: (1)shrinkage—important during each phase of fabrication; and (2) absorptionand density through vitrification (absorption); and (3) strength—green,bisque and fired.

In order to prepare a ceramic article in accordance with the presentinvention, an example of the object may be imaged using either 2D or 3Dimaging techniques in order to obtain a computer files or datarepresentative of the object and adapted to be used to guide the 3DPmachine. This may be done for instance using a scanner such as theZScanner 700 commercially available from Z-Corp. One may extrapolatefrom 2D imaging for this purpose.

A 3DP machine, such as the ZPrinter 310 Plus, commercially availablefrom Z-Corp is loaded with the ceramic powder and the binder inaccordance with the present invention. The computer file(s) to guide thelayered deposition are transferred to the machine and the machinedeposits alternately layers of the binder and ceramic power such that aceramic precursor of the desired shape is formed though the computerguidance obtained from the scanner. Computer instructions may also beconverted from CAD files of the desired shape, such as by use of theZPrint Software, commercially available from Z-Corp.

Typically and preferably, this is done with one-to-one ratio of thebinder and ceramic powder, alternating one atop the other, althoughother layering arrangements may be found effective to create a precursorshape.

After the ceramic precursor of the desired shape is formed, it may befired and/or glazed in accordance with methods and apparatus known andused in the art.

In the case of a teapot, the pot and cover may be scanned and depositedas individual pieces.

The present invention may be also demonstrated by the use of a basicstandard test bar that may be used to measure the properties of theprecursor through each stage of the process. Examples are seen in FIG.13. A virtual model of a test bar may be rendered in multiples each timematerial is run through the machine. Given that many test bars can bemade during each run of the printer, it will be possible for instance tocreate a fine art object and five test bars in one printing session.Below is a description of each component.

Shrinkage

Each bar will have a 10 cm demarcation rendered directly into the bar.The bars may be measured after each process of air-drying, bisquefiring, and final firing. The difference of the various measurementsprovides crucial data for shrinkage in a manner consistent with industrystandards for all ceramic applications. The data for each formulamodification may then be logged into a database and then compared toother known industry formulas. This will allow for one to control forshrinkage by preparing ceramic precursor articles with the amount ofshrinkage to be allowed for, such that the desired accurate shape andsize of the finished ceramic piece may be achieved. This may be doneeither in cases where the shrinkage of the unfinished (unfired) articleplaces the article still within desired manufacturing tolerances, or incases where the shrinkage of a given precursor binder-powder formulationis known such that it may be considered so as to arrive at the desiredsize of the finished article.

Absorption and Density

In order to determine the absorption and density of the precursorarticle made in accordance with the present invention, each bar will maybe weighed immediately as it is removed from the printer. This baseweight contains the total wet weight of the object. The bar may then beweighed after it has completely air-dried. (A small dryer may be used toeliminate variations in ambient air humidity, if desired). Thedifference between the dry weight and the wet weight will indicate theamount of liquid (in the binder) used to bind the powder, which isneeded to determine the effects of different binder recipes and tomeasure consistency in the printing process. To determine the absorptionof the sample, each bar may be weighed after it has been fired to aspecific temperature, soaked for twenty-four hours in water, and weighedagain. The tests may then be boiled for about two hours and weighedagain; this will measure the coefficient of expansion, which isimportant information for clays that will be placed outdoors and inother harsh environments. The parameters of this test are known and usedin industry.

Strength Testing

It typically will be important to monitor is green strength; i.e., isthe object rendered durable enough to be handled after it is removedfrom the printer and placed in the kiln? It is preferred that theceramic precursor objects in the green state be strong enough to behandled to be safely placed in the kiln. This strength is directlyrelated to the effectiveness of the binder and can easily be measured bythe following simple test. The bar may suspended on both ends and weightis incrementally applied to the center of the bar until it fails. Thesame test may be applied to the bar after firing to determine basicfired strength data. Bars of the same size and shape may be made withtraditional fabrication methods and a known formula to establish abase-line measurement for comparison in further experiments. Eventuallythe best of the formulas may be sent to a ceramic lab to find thespecific “Modulus of Rupture”. These data may then be compared withindustry parameters for the object to be produced, if desired. Thistesting may confirm what is already observed in ceramic precursorsproduced in accordance with the present invention, and may be able toquantify it with industry standards.

Variations may be made from the preferred ceramic powder and binderformulation as desired for various applications. It is preferred thatall tests be controlled and logged with all information needed forreplication and confirmation. It is preferred that one not make changesboth to the binder and the formula for each run as it is preferred tomaintain one variable constant. That is, if one changes a material orits ratio in the clay formula, preferably one must measure it using thesame binder. Likewise, if one changes the binder, one should comparethose results on the same formula. While this complicates the testingprocedures, it is possible to do given that effective binders andceramic powder formulas are disclosed herein. It is important to notethat all of the clay formulas may consist of materials that have beentested and chemically analyzed using a computer program that containsthis information and can instantly calculate the molecular formula ofany combination of the possible ingredients. Such computer programs aretypically used in glaze and clay body calculations.

This testing provides crucial information as to the viability ofspecific formulas and binders. In addition to the tests described above,other tests may be done related to various ceramic processes includingglazing and pyroplasticity (warping during firing). Some test bars maybe glazed using various techniques and process and measured for “glazefit” and other important phenomena related to potential applications ofthe present invention.

FIG. 13 is a perspective view of a series of test bars produced inaccordance with the method of the present invention. Table 1 containsdata from several test runs using the method of the present invention.Some of the significant aspects of the results reported in Table 1 arethe reduced amount of shrinkage achieved through the method of thepresent invention, even without using the layer compression method ofthe present invention. The significant aspects of the results includethe reduction in distortion and friction cracks.

The present invention also includes a three-dimensional printingapparatus and printing method.

Referring to the Figures, FIG. 1 shows three-dimensional printing device1 having supply bed 2 and build table 3.

Powder transport unit 4 is also bears reciprocating binder print head 5.

On the trailing portion of powder transport unit 4 is compressor platemechanism 6 which includes compressor plate 7 and actuator arms 8.

In operation, powder transport unit 4 reciprocates between the positionA as shown in FIG. 1 and position B as shown in FIG. 2. As the powdertransport unit 4 moves from position A to position B, it takes ceramicpowder from supply bed 2 and deposits a layer of ceramic powder acrossbuild table 3.

Powder transport unit 4 then reverses direction across build table 3whereby reciprocating binder print head 5 deposits a layer of bindersuch as described herein.

This process is repeated as the build table is lowered to build athree-dimensional ceramic precursor article.

Following each successive deposit of a layer of powder (where powdertransport unit 4 reaches position B), compressor plate 7 borne byactuator arms 8 provides a compressing downward tamping to eachsuccessive binder/powder layer as it is formed. This may be seen byreference to the position of compressor plate 7 and actuator arms 8 inFIGS. 2 and 3. The compressor plate 7 in its lowered position may alsobe seen in FIGS. 4-6. This has the effect of making the composite greenarticle so formed better able to maintain its green strength, whileultimately leading to the production of a stronger ceramic piece as theconstituent materials are placed in more intimate contact between thebinder and powder layers before firing.

The action of the compressor plate 7 and actuator arms 8 may becontrolled by an electronic actuator subject to algorithmic control. Aseach layer is placed and reduced in thickness by compression, thealgorithmic controller adjusts the subsequent layer to be deposited inorder to accommodate for the vertical displacement of each layer in thecross-sectional series of deposition. That is, as each binder/powderlayer is compressed, the height of the article thus far produced isreduced from where is otherwise would be prior to compression.Accordingly, the programming algorithm controls the deposition toaccommodate the resultant height of the post-compression article indetermining the pattern to be laid in the next sequential deposit. Thismay be accomplished by amendments to the computer programming used incurrent three-dimensional printing devices to make mathematic changes toaccommodate the regression in the cross-sectional series brought aboutthrough the known amount of thickness reduction brought about bycompression.

FIGS. 4-6 show detailed views of the compressor plate 7 and actuatorarms 8 in more detail, with the compressor plate 7 in its loweredposition, as seen in FIG. 3. FIG. 4 shows the tamping mechanism withcover 9, while FIGS. 5 and 6 show views with cover 9 removed. TheseFigures also show gears 11 and 12 (which may also be friction wheels asan alternative), as well as electric motor 13 which turns shaft 14 so asto provide light tamping displacement against the sequential layers ofthe ceramic precursor as it is being built in sequential layers in buildtable 3.

FIG. 7 shows the compressor plate 7 and actuator arms 8 in a raisedposition after the protective cover 10 of three-dimensional printingdevice 1 has been raised. This allows for the removal of the finishedceramic precursor piece for clean-up and firing.

The present invention may be used in a wide variety of artistic andindustrial applications. One such application is in the area of ceramicfilters. Ceramic articles of the present invention have been found tohave relatively uniform porosity, such that they may find advantageoususe as ceramic filters in a wide variety of industrial applications.

Still another application of the present invention is to providereplacement parts for ceramic constructions, industrial or artistic,where a piece has become broken or lost altogether. For instance, inpreparing filler pieces to display archeological ceramics to be able tosupport and secure such items, the missing portion(s) may be obtainedthrough digital scanning, and the missing piece prepared using themethod of the present invention. Likewise, broken or missing industrialceramic articles may be repaired or replaced, for instance by scanning abroken insulative tile to obtain a 3D digital image of the missingportion of the tile, in order to provide a replacement piece sized tofit precisely the space requiring repair.

Because the present invention allows for the direct and true-to-sizecreation of finished ceramic articles, one may create customized ceramicarticles to fit or retrofit industrial, artistic or archeologicalarticles, arrangements and installations efficiently.

An example of a ceramic object (i.e., a hand rendered ceramic) that maybe reproduced in accordance with the present invention is shown in FIG.8. FIG. 9 shows a perspective view of a fired ceramic object made fromthe three dimensional digital rendering and printing process of thepresent invention as applied to the ceramic object of FIG. 8. FIG. 10shows a comparative perspective view of the original ceramic objectshown in FIG. 8 and the finished ceramic object produced in accordancewith one embodiment of the present invention shown in FIG. 9.

Other examples of finished ceramic articles made in accordance with themethod of the present invention and that would otherwise be impossibleto make through standard molding techniques, owing to the presence ofundercut in the piece, are shown in FIGS. 11 and 12.

All of the patents and other publications referred to herein are herebyincorporated herein by reference.

What is claimed is:
 1. A ceramic precursor article having apredetermined shape, said article comprising alternately depositedlayers of (1) a ceramic precursor powder comprising from about 50% toabout 80% clay, from about 5% to about 20% feldspar, from about 2% toabout 10% refractory cement, from about 2% to about 10% frit, and fromabout 0.5% to about 4% sodium silicate and (2) a binder comprising waterand polyvinyl alcohol, in a pre-determined pattern, such that saidceramic precursor article is of said predetermined shape.
 2. A ceramicprecursor article according to claim 1 wherein said binder comprisespolyvinyl alcohol having a molecular weight in the range of 7,000 toabout 15,000.
 3. A ceramic precursor article according to claim 1wherein said binder comprises polyvinyl alcohol having a molecularweight in the range of from about 9,000 to about 10,000.
 4. A ceramicprecursor article according to claim 1 wherein said binder comprisespolyvinyl alcohol having a degree of hydrolysis in the range of fromabout 65% to about 95%.
 5. A ceramic precursor article according toclaim 1 wherein said binder comprises polyvinyl alcohol having a degreeof hydrolysis in the range of from about 75% to about 85%.
 6. A ceramicprecursor article according to claim 1 wherein said binder comprisespolyvinyl alcohol, at least one humectant and at least one flow agent.7. A ceramic precursor article according to claim 1 wherein said binderis substantially free of cellulose.
 8. A ceramic precursor articleaccording to claim 1 wherein said binder comprises polyvinyl alcoholfrom about 60 to about 80%, glycerol from about 15 to about 25% andethylene glycol from about 5 to about 15% by weight of the binder absentwater.
 9. A ceramic precursor article according to claim 1 wherein saidbinder comprises polyvinyl alcohol from about 70 to about 75%, glycerolfrom about 15 to about 25% and ethylene glycol from about 5 to about 15%by weight of the binder absent water.
 10. A ceramic precursor articleaccording to claim 1 wherein said ceramic article shrinks less than 15%as compared to its actual size upon being subjected to sufficient heatto form a ceramic article therefrom.
 11. A method of preparing a ceramicarticle of a desired final shape comprising: (a) alternately depositinglayers of (1) a ceramic precursor powder comprising from about 50% toabout 80% clay, from about 5% to about 20% feldspar, from about 2% toabout 10% refractory cement, from about 2% to about 10% frit, and fromabout 0.5% to about 4% sodium silicate and (2) a binder comprising waterand polyvinyl alcohol, in a pre-determined pattern so as to form aceramic precursor article of a precursor shape from a plurality of saidlayers, and (b) subjecting said ceramic precursor article to heat forsufficient time to form a ceramic article of said desired final shape.12. A method according to claim 11 wherein said binder comprisespolyvinyl alcohol, at least one humectant and at least one flow agent.13. A method according to claim 11 wherein said binder is substantiallyfree of cellulose.
 14. A method according to claim 11 wherein saidbinder comprises polyvinyl alcohol from about 60 to about 80%, glycerolfrom about 15 to about 25% and ethylene glycol from about 5 to about 15%by weight of the binder absent water.
 15. A method according to claim 11wherein said binder comprises polyvinyl alcohol from about 70 to about75%, glycerol from about 15 to about 25% and ethylene glycol from about5 to about 15% by weight of the binder absent water.
 16. A methodaccording to claim 11 wherein said ceramic article shrinks with respectto the size of said ceramic precursor article less than 15%.
 17. Amethod according to claim 11 wherein said desired final shape differsfrom said precursor shape by less than 10%.
 18. A ceramic article madeby the method of claim 11.